1. Field of the Invention
This invention relates to the art of adjustable position electronic depth finders or SONAR depth sounders for use in water by pleasure boating enthusiasts and serious fishermen as a navigational aid and as a fish finder so as to overcome underwater blindness. This invention can be used as a tool to serve as eyes and ears under the water.
2. Description of the Prior Art
Electronic depth finders or SONAR transducer depth sounders have been known and used for many years. They are also called by various other names; such as depth flasher, fish locator, fish flasher, depth meter, depth recorder and scanning SONAR.
SONAR was introduced around the time of World War II. The word SONAR is an acronym for "sounding, navigation and ranging." A sound tone is created electronically and sent out into the water in a cone-like fashion. The speed of sound in water is about 4,950 feet per second. When that sound wave hits a solid object, part of the sound is reflected back to the source as an echo. By carefully timing how long it takes for the echo to return, it is possible to determine the distance between the object and the source.
The relatively low cost electronic depth finders that are widely used today by avid fishermen employ a main battery operated control box located in the boat and having an electronic device that creates an electrical impulse which travels from the main box through an electrical cable to a transducer device that is generally placed in the water. The transducer is a controlled sound wave energy transmitter and receiver that converts the electrical impulse into a high frequency sound impulse that is inaudible to the fish as well as to humans. The transducer may be aimed at the bottom of the body of water, or at a rock, at a sunken tree, or a school of fish. The echo bounces back to the transducer which reconverts that sound back into an electrical impulse which shows up on a dial that reads directly in feet or fathoms. The main box may include a volume sensitivity or gain control so that the sound signal may be adjusted loud enough to bounce back an echo if the water is very deep or the body of water has a soft mud bottom which tends to absorb the sound.
There are five main types of control box and read-outs for electronic depth sounders: (1) the flasher unit is the most popular type of sounder and it employs a motor driven wheel which supports a flashing neon bulb or light emitting diode which flashes about 24 impulses per second, and displays the bottom depth in terms of a band of light on a calibrated dial, (2) the meter unit employs a needle in combination with a dial, (3) the recorder or graph unit interprets the signal for the operator and actually draws or prints out a permanent picture of the bottom showing the slopes and drop-offs, boulders, trees and fish, (4) combination flasher-recorder units provide the speed reading of the flasher unit and the means of obtaining a detailed graph of an unusual formation, (5) the scanning SONAR unit is for commercial fishermen and charter boats and it scans a 360.degree. circle and the conditions may be read on a graph or recording type instrument or on a direct read-out on the face of a cathode ray tube, which is the same as a TV picture tube.
The Lowrance Electronics Mfg. Corp. of Tulsa, Okla. probably introduced the first electronic depth finder for consumer use; known as the FISH LO-K-TOR.
In the past, the transducers were either fixedly mounted to the stern of the boat beneath the water line, or mounted at the bottom of a vertical shaft that has a mounting bracket fastened to the transom or gunwale of the boat. This vertical shaft is rotatable about a vertical axis for 360.degree. scanning horizontally.
The Mayes U.S. Pat. No. 2,837,727 discloses a general type of adjustable position vertical shaft for mounting a hydrophone below water.
Another front-end mounting location for the transducer has been to the keel of an electric trolling motor at about a 45.degree. angle to the vertical axis of the supporting shaft of the motor so the transducer may be rotated through an angle of 360.degree..